The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
For example, lithography is a technique frequently used in IC manufacturing for transferring an IC design to a semiconductor substrate. A typical lithography process includes forming a hard mask layer over a substrate, patterning the hard mask layer to form a hard mask, and etching the substrate using the hard mask as an etch mask. Patterning the hard mask layer typically includes coating a resist (or photoresist) over the hard mask layer, exposing the resist to a radiation such as deep ultraviolet (DUV) ray or extreme ultraviolet (EUV) ray, and developing and partially stripping the resist to leave a patterned resist over the hard mask layer. The patterned resist is then used in subsequent etching of the hard mask layer to form the hard mask. As the device miniaturization continues, there is frequently a need to produce island type small hard masks.